South Yorkshire Police chief constable David Crompton said the 'expanding nature' of the investigation meant he could not give a date when it would be concluded.

In a letter to Keith Vaz, chairman of the Commons Home Affairs Select Committee, Mr Crompton said the force was in regular contact with Sir Cliff's lawyers.

A statement released by Sir Cliff tonight said: "I have no idea where these absurd and untrue allegations come from.

"The police have not disclosed details to me. I have never, in my life, assaulted anyone and I remain confident that the truth will prevail. I have co-operated fully with the police, and will, of course, continue to do so.

"In the meantime, I would, again, like to thank everyone for supporting me through this unbelievably difficult period."

The publication of the letter from Mr Crompton, dated February 10, followed a scathing independent report into an agreement between South Yorkshire Police (SYP) and the BBC which led to a raid on the singer's home being broadcast live around the world.

(Image: PA)

The independent report found that the deal "certainly interfered with his privacy and may well have caused unnecessary distress".

Following the raid, Sir Cliff was interviewed by detectives investigating a claim of a sex crime involving a young boy, but was not arrested or charged.

Former chief constable Andy Trotter said SYP should never have a made a deal with the broadcaster - a decision taken after BBC reporter Dan Johnson went to the force saying he knew they were investigating the veteran entertainer.

Mr Crompton said a Metropolitan Police investigation into the source of the leak to the BBC had been unable to find the source.